1. Field of the Invention
The present invention relates to a roller bearing and, more particularly, to a roller bearing suitable for rotating shafts, such as a crankshaft and a camshaft, disposed in engine housings.
2. Related Art
Recently, roller bearings have generally been used for rotatably supporting rotating shafts, such as a crankshaft and a camshaft, disposed in engine housings (e.g., a cylinder block and a cylinder head). In such a case, an inner ring of the roller bearing can be omitted therefrom by utilizing the outer peripheral surface of the rotating shaft directly as a raceway surface. Thus, the diameter-reduction (miniaturization) of the roller bearing can easily be achieved by simultaneously maintaining load capacity. However, because the bearing, from which the inner ring is omitted, lacks a means for fixing the bearing to the rotating shaft, it is necessary to restrict the axial displacement of a cage. Further, in the case of such a rotating shaft, a large centrifugal force acts upon the roller bearing with engine rotation. Thus, it is also necessary to consider the radial displacement of the cage. Especially, in the case of a crankshaft, the outer ring of the bearing is split into two parts, there is a fear that when the cage is moved (displaced) in an axial direction and a radial direction so as to touch an outer-ring splitting position, an excessive internal stress is generated in the cage.
Thus, the following technique is disclosed (see, e.g., JP-A-2006-322581). That is, a convex portion that outwardly and radially protrudes is provided at each of both axial end portions of the cage. The convex portions of the cage are mounted along the end surfaces of the split outer ring, respectively, so as to restrict the axial displacement of the cage.
According to JP-A-2006-322581, the convex portions of the cage rotate while contacted with the end surfaces of the split outer ring. Thus, there are still fears that a torque loss may be caused due to the sliding resistance generated therebetween, and that excessive internal stresses may be generated in the cage. Additionally, the radial displacement of the cage due to the centrifugal force due to the engine rotation is not sufficiently considered.